Cd Vacancy Engineered CdS/Ti ₃ CN Heterostructure for High‐Performance Photocatalytic Oxidation of Thioethers to Sulfoxides Under Visible Light

Traditional sulfoxide synthesis often relies on toxic oxidants and harsh conditions. Photocatalytic oxidation using inorganic semiconductors provides a greener approach but is limited by low catalytic efficiency. Herein, we developed a heterostructure catalyst enriched with cadmium vacancies (denoted as Cd_vS_x/Ti₃CN). The optimized Cd_vS₄/Ti₃CN exhibited a high sulfoxide production rate of 21.85 mmol·g_cat ^-1·h^-1, outperforming most reported catalytic systems. Comprehensive characterization revealed that sulfur dosage was precisely tuned during synthesis to generate abundant cadmium vacancies and expose active crystal facets. In particular, the presence of cadmium vacancies enhances substrate adsorption via unsaturated coordination sites, lowers the energy barrier for bond activation, and promotes the activation of O₂ into superoxide radicals. Moreover, Ti₃CN further facilitates photogenerated electron transfer and enhances superoxide radical concentration by enabling favorable band alignment with CdS. In addition, the catalyst demonstrates excellent substrate compatibility and recyclability. This work offers a new approach for improving the performance of CdS-based inorganic semiconductor catalysts in sulfoxide synthesis through Cd defect engineering.